Multi-role aircraft with interchangeable mission modules

ABSTRACT

A flight-operable, truly modular aircraft has an aircraft core to which one or more of outer wings members, fuselage, cockpit, leading and trailing edge couplings, and empennage and tail sections can be removably coupled and/or replaced during the operating life span of the aircraft. In preferred embodiments the aircraft core houses the propulsive engines, avionics, at least 80% of the fuel, and all of the landing gear. The aircraft core is preferably constructed with curved forward and aft composite spars, that transfer loads across the center section, while accommodating a mid-wing configuration. The aircraft core preferably has a large central cavity dimensioned to interchangeably carry an ordnance launcher, a surveillance payload, electronic countermeasures, and other types of cargo. Contemplated aircraft can be quite large, for example having a wing span of at least 80 ft.

This application claims priority to U.S. Provisional Application No.61/372,941 filed Aug. 12, 2010, and U.S. Utility application Ser. No.13/205,870, filed Aug. 9, 2011, each of which is incorporated byreference herein in its entirety.

FIELD OF THE INVENTION

The field of the invention is aircraft.

BACKGROUND

Aircraft development is a capital-intensive and usually lengthy process.Further, because the viability of aircraft depends largely on theirweight, conservatism in design can have powerful consequences on theviability of an aircraft. As a result of these two factors and otherconsiderations, any given aircraft tends to be specialized for one roleor mission during the design process.

At the same time, aircraft are used on and needed for a variety ofmissions and roles. Aircraft carry different payloads, including forexample, passengers, cargo, sensors, and munitions. Beyond payload,other requirements can shape an aircraft design; for example, somemissions require flight in a certain speed regime, while other missionsrequire high fuel efficiency.

Prior art approaches to providing aircraft suitable for conductingspecific missions tend to either (i) design a distinct aircraft for aspecific mission, (ii) adapt an existing aircraft design for anothermission through modifications (iii) attempt to bridge multiple missionsin the design stage through an a priori requirement.

Each of these three prior art approaches has weaknesses. The firstapproach, to design a distinct aircraft for a specific mission, isextremely expensive and often impractical. In general, it has the leastpotential to meet multiple diverse requirements, therefore limiting itsmarket. The second approach, post-hoc adaptation, is often used inadapting aircraft to new missions similar to the original designmission. Even this approach is expensive and time consuming, however.These difficulties arise in part because of formidable certification andqualification requirements. An example of aircraft post-hoc modificationis the transformation of the Lockheed L-188 Electra civilian passengertransport into the Lockheed P-3 Orion naval maritime surveillanceaircraft. The original mission (passenger transport) and the new mission(maritime surveillance) have similar flight envelope requirements, interms of speed and altitude.

The third general approach, attempting bridge multiple missions in thedesign stage through an a priori requirement, often entailsextraordinary costs and engineering effort. An example of this approachwould be the Lockheed Martin F-35 family of supersonic fighter aircraft,attempting commonality between the F-35B short takeoff and verticallanding (STOVL) platform, the F-35C carrier based fighter platform, andthe F-35A land-based conventional takeoff supersonic fighter platform.The F-35 program is renowned for being billions of dollars over budgetand years behind schedule; this results at least in part from attemptsto achieve high degrees of commonality among the aircraft in the family.The Boeing competitor to the F-35, as described in U.S. Pat. No.5,897,078 struggled with similar issues in attempting to bridge diversemission requirements, while still retaining some degree ofparts-commonality among variants.

The '078 patent and all other extrinsic materials discussed herein areincorporated by reference in their entirety. Where a definition or useof a term in an incorporated reference is inconsistent or contrary tothe definition of that term provided herein, the definition of that termprovided herein applies and the definition of that term in the referencedoes not apply.

In summary, aircraft are sometimes designed to be flexible, yet thisby-design flexibility can only go so far. Alternatively, differentversions of aircraft are designed for specific needs, users, andmissions. Only a few prior art aircraft and aircraft relateddevelopments known to the inventor have had elements of modularity, andno known prior art aircraft have achieved complete or even extensivemodularity.

A few cargo aircraft have carried their cargo in removable cargocontainers. Notably, the Fairchild XC-120 Packplane, Miles M.68 Boxcar,and Kamov KA-226 are the instances known to the inventor. FIG. 1Aillustrates the Kamov KA-226 helicopter 110, which features a mainportion 112 of the aircraft and a removable cargo container 114, whichcan be configured to carry passengers. FIG. 1B is a side viewillustration of the Miles M.68 Boxcar 120, which is a fixed-wingtransport aircraft having a main portion 114 of the aircraft, andconfigured to carry cargo in a removable cargo container 124.

While these prior art aircraft carry their cargo payload in removablecontainers, they cannot be said to be truly modular aircraft, becausethey do not change containers to change missions or roles. These priorart aircraft are really predominantly single-role transport aircraftthat happen to carry their cargo in an external container that formspart of the aerodynamic fairing of the aircraft, rather than carryingtheir cargo in containers internal to the aerodynamic fairing of theaircraft like most air freighters.

Aircraft designed to have large cargo bays also do not lend themselvesto modularity because the wings need to have structural support acrossthe fuselage. Such structural supports are either positioned above thefuselage (in a high wing configuration) or below the fuselage (in a lowwing configuration). In either of those configurations it is notpractical to provide readily replaceable wings.

In a similar vein, but for a different kind of aircraft, U.S. Pat. No.4,736,910 to O'Quinn is directed to a light fighter aircraft withinterchangeable nose and tail sections. U.S. Pat. No. 3,640,492 isdirected to aircraft having electronics or avionics equipment inremovable portions of the aircraft structure or aerodynamic fairing.U.S. Pat. No. 7,234,667 to Talmage describes the division of an aircraftinto sections, any of which could be recovered by parachute following anin-flight incident. U.S. Pat. No. 6,098,927 describes an aircraft with aremovable fuselage section to increase or decrease the payload capacityof the aircraft. Related to this idea, the practice of extending orcontracting fuselage sections by the addition or removal of fuselageplugs is known in the art, and is commonplace in stretched families oftransports, including for example, the Airbus A318, A319, A320, andA321, which are substantially just stretched versions of the sameaircraft accommodating 107-220 passengers. Unless the context dictatesthe contrary, all ranges set forth herein should be interpreted as beinginclusive of their endpoints, and open-ended ranges should beinterpreted to include only commercially practical values. Similarly,all lists of values should be considered as inclusive of intermediatevalues unless the context indicates the contrary.

US Patent Application 2008/0017426 describes a somewhat modular groundvehicle, wherein a core vehicle can attach to a variety ofinterchangeable elements to serve different roles or missions. However,it should be noted that the field of ground vehicles is substantiallydifferent from the field of aircraft, and that aircraft are subject tostricter design constraints. For example, aircraft are highly weightsensitive and aerodynamic drag sensitive and poorly tolerate structuraland powerplant inefficiencies, such as those built into the groundvehicle of 2008/0017426 for modularity. A person of ordinary skill inthe art would not expect systems and methods that work on groundvehicles to also work on aircraft without significant additionalinventive subject matter.

It should be noted that a key constraint for adapting aircraft to servedifferent roles and missions is the operator interface. As an example,consider the vastly different pilot interfaces found among helicopters,transport aircraft, fighter aircraft, and the ground stations ofunmanned aircraft. If an aircraft is to serve multiple roles andmissions, it must have a suitable and adaptable interface. This is aformidable challenge, and relatively little known prior art addressesthis challenge.

U.S. Pat. No. 5,626,030 to Watson describes a ground-based flightsimulator that uses parts of an actual aircraft. However, this referencedoes not provide a ground control station for an aircraft that is commonto a cockpit of an aircraft. U.S. Pat. No. 5,880,669 to Romanoff, et al.also describes an aircraft simulator system, but does not disclose aground control station for an unmanned aircraft that is substantiallyidentical to a cockpit for a manned aircraft.

Thus, there is still a need for aircraft that are quickly andeconomically adaptable to different roles and missions, not simplyadaptable to different payloads—aircraft that are both modular andmultirole.

SUMMARY OF THE INVENTION

The inventive subject matter provides apparatus, systems and methods ofa flight-operable, truly modular aircraft.

In a first aspect, a modular aircraft combines an originally deployedwing member that provides at least 15% of the lift during at least someportion of cruise flight, a center section that provides at least 25% ofthe aircraft during such flight, and has one or both of (a) a forwardcoupling adapted to couple or decouple a fuselage to the center sectionduring the operational life, and (b) a wing coupling adapted to coupleor decouple the wing member during the operational life. Detachableleading and trailing edge couplings can be applied to the centersection, and preferably assist in providing lift.

In this first aspect, the fuselage is optional, and where the fuselageis present, it may or may not include a cockpit. Although the aircraftmay be shaped as a flying wing, having substantially no empennage, nohorizontal tail, and no vertical tail, the optional fuselage may includean empennage, a horizontal tail, and/or a vertical tail.

Modularity can be achieved to a large extent by incorporating manycomponents into the center section. For example, the center section canadvantageously contain a propulsive engine, disposed so that it does notextend above or below the center section. In some contemplatedembodiments, there are first and second engines disposed on oppositesides of the central cavity. The center section preferably houses atleast 80% of all of the fuel, and the aircraft may have a fuel capacitygreater than maximum takeoff weight.

The center section can also advantageously include avionics sufficientto operate the aircraft without receiving controls from outside thecenter section. In some embodiments, it is contemplated that theavionics can operate the aircraft through either or both of groundcontrol and an on-board pilot control. Additionally or alternatively,the center section can include an on-board pilot interface. The centersection can also advantageously receive one or more, and preferably allof the retracted landing gear for the aircraft.

In preferred embodiments, the center section is constructed in a mannerthat produces a centerline central cavity. This can advantageously beaccomplished using forward and aft curved composite spars, and right andleft inboard ribs. the central cavity can be quite large, for examplehaving a width dimension at least 3% of the span of the aircraft, and alength dimension at least 20% of the length of the aircraft. Not only isthe central cavity large horizontally, but it can be large vertically,preferably extending all vertically all the way to the upper skin andlower skins of the aircraft. The central cavity can also advantageouslyhave a cargo dimensioned to interchangeably carry an ordnance launcher,a surveillance payload, and electronic countermeasures.

By placing so much of the flight-critical components in the centersection, the wings (or outer wing sections) can be detachable. Forexample, a detachable wing member having a composite wing spar cancouple to the forward and aft spars of the center section using a wingcoupling with one or more hardpoints. The wing coupling can carryelectrical connections between the center section and the wing member,and in some contemplated embodiments the wings can be hingedly coupledto the center section. Whether or not the wings are detachable, it iscontemplated that they can be quite large. For example, aircraftcontemplated herein can have a wing span of at least 80 ft, with leftand right outer wing members having sufficient stiffness to produce anatural frequency of no less than 6 Hz when airborne.

Other hardpoints are contemplated that removably couple a cockpit moduleto the center section during an operational life of the aircraft, andthat removably couple a tail section to the center section during anoperational life of the aircraft.

Various kits are contemplated with one or more of the features discussedabove. For example, kits are contemplated that comprise a fuselage, thatinclude a replacement wing member that is not fungible with theoriginally deployed wing member, that include replacement leading and/ortrailing edge portions, and that include center sections havinghorizontally curved forward and aft composite spars.

In a second aspect, a modular aircraft having originally deployed wingmember that provides at least 20% of the lift of the aircraft during atleast some portion of cruise flight has (a) center section that includesa centerline cavity, and avionics sufficient to operate the aircraft;(b) a forward coupling adapted to couple or decouple a forward componentto the center section during the operational life; and (c) a wingcoupling adapted to couple or decouple the wing member during theoperational life. The aircraft can have any one or more of the featuresdiscussed above.

In a third aspect, a modular aircraft has a center section with a largecargo bay, and left and right wings that are structurally coupledtogether at least predominantly using supports positioned fore and aftof the cargo bay, rather than above or below the cargo bay. This allowsthe wings to be coupled to the center section in a mid wingconfiguration, without adding undue weight to the aircraft. In apreferred mid wing aircraft described below, the cargo bay is at least 6feet wide, at least 14 feet long, and at least 10 feet high. Morepreferably, the cargo bay is at least 8, or at least 10 feet wide,independently at least 16, at least 18, or at least 20 feet long, andindependently at least 12, at least 14, or at least 16 feet high.

Various objects, features, aspects and advantages of the inventivesubject matter will become more apparent from the following detaileddescription of preferred embodiments, along with the accompanyingdrawing figures in which like numerals represent like components.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1A is a side view drawing of a prior art rotorcraft with aremovable cargo container, while FIG. 1B is a side view drawing of aprior art fixed-wing airplane with a removable cargo container.

FIG. 2 is a schematic perspective illustration of a preferred modularaircraft kit comprising a center section, various outer wing portions,and various mission modules.

FIG. 3 is a perspective exploded view illustration of an alternatepreferred aircraft center section showing the supporting structure andkey mechanical systems.

FIG. 4 is a schematic top-view illustration of a preferred modularaircraft.

FIG. 5 is a schematic top-view illustration of an alternateconfiguration of the preferred modular aircraft of FIG. 4.

FIG. 6 is plot of the lift distribution of the preferred modularaircraft of FIG. 5.

FIG. 7 is a perspective view illustration of an exceptionally preferredaircraft left interface assembly.

FIG. 8 is a perspective view illustration of an exceptionally preferredforward and aft center section hardpoints.

DETAILED DESCRIPTION

Along with the drawing, the following detailed description serves toelucidate various aspects of the present inventive subject matter.

FIG. 2 is a schematic perspective illustration of a preferred modularaircraft kit comprising a center section, various outer wing portions,and various mission modules.

The modular aircraft kit 200 comprises a center section 210. The centersection 210 advantageously features a left interface 215 for a leftouter wing member and a right interface 216 for a right outer wingmember. In especially preferred embodiments, the left and rightinterfaces 215, 216 are hardpoints configured to allow folding orremoval of the outer wing members for compact stowage. The centersection 210 is preferably equipped with provisions for propulsive means.A right engine housing 218 and a left engine housing 217 each fair overan inlet, turbofan engine, and exhaust. When coupled to electric power,a flight control system, and a fuel supply, the engine is capable ofproducing thrust for sustained flight of the modular aircraft. Thecenter section 210 also has a substructure consisting of one or morespars and ribs (not shown). In preferred embodiments, removableaerodynamic or structural elements are attached to this substructure.Center section 210 is equipped with a right leading edge portion 211, aleft leading edge portion 212, a right trailing edge portion 213, a lefttrailing edge portion, and one or more center panels 207. By removing orreplacing the center panels 207 and other interchangeable elements,other mission modules or fuselages can be accommodated. The centersection 210 also comprises a right wing member 209 and a left wingmember 208 for generating lift. Internal to the center section 210 are anumber of aircraft systems essential to flight.

A preferred manned aircraft 220 is advantageously composed of elementsof the modular aircraft kit 200. A center section 210 is configured tosupport a fuselage 227 featuring a cockpit 228. The cockpit 228advantageously includes provisions for a human pilot including anejection seat, flight controls, an environmental control system,avionics, a clear windscreen or canopy, and instrumentation. The centersection 210 supports a right outer wing member 222 comprising rightcontrol surfaces 223 attached at the right interface 216 for an outerwing in a manner that supports folding of the right outer wing member222. Similarly, the left outer wing portion 224 has left controlsurfaces 225 and is attached at the left interface 215 with the centersection. The preferred manned aircraft 220 has no tail surfaces,empennage, horizontal tail, or vertical tail. All aircraft control isaffected via control surfaces 223, 225 located on the right and leftouter wing members 222,224. Also shown is landing gear 226 in anextended position, which advantageously retracts into the centersection. To install the fuselage 227, which can be viewed as a missionmodule, the center panel 207 and other parts of the center section areremoved (or alternately, are never installed) from the center section210. The fuselage 227 is structurally attached at hardpoints (not shown)and electrical connections are made facilitate power and data signalsbetween the fuselage 227 and center section 210. Similarly, electricalconnections are made between the outer wing members 222, 224 and thecenter section 210. In preferred aircraft, control surfaces 223, 225 areelectrically actuated, but other actuation means such as hydraulic,mechanical, and pneumatic are also contemplated.

A preferred unmanned aircraft 230 is also composed of elements of themodular aircraft kit 200. In this case, the center section 210 isconfigured to support a mission module 237 advantageously containingpayload and mission equipment, including, for example, elements selectedfrom the list containing sensors, cameras, cargo, munitions, firesuppressant, datalinks, antennas, and radio communications equipment.The same outer wing portions 222, 224 are attached to the center section210 as for the manned aircraft 220. Indeed, the only difference betweenunmanned aircraft 230 and manned aircraft 220 is the selection andinstallation of mission module 237 and fuselage 227, respectively.Unmanned aircraft 230 features the same landing gear 226, engines,control surfaces, and systems as manned aircraft 220. Unmanned aircraft230 is advantageously equipped with a flight control computer containingflight control laws allow autonomous flight without human intervention.Unmanned aircraft 230 is also advantageously equipped with one or moredatalinks (not shown) mounted in the mission module 237 or centersection 210 allowing control via remote ground control station (notshown). Some preferred aircraft may comprise elements of U.S.application Ser. No. 11/506,571.

In preferred modular aircraft kits, other (not originally deployed)mission modules would also be installable in the center section 210. Forexample, a cargo module 240 would interface with center section 210 viastructural hardpoints 243 and an electrical interface 245. The cargomodule 240 could comprise a hatch portion 244 for loading or unloadingcargo, and an empennage comprising a vertical tail 241 and a horizontaltail 242. Other cargo modules are also contemplated with no empennagewherein all flight control and stability assurance are obtained viacontrol surfaces located on outboard wing portions.

An alternate unmanned aircraft 250 is also composed of elements of themodular aircraft kit 200. In this case, the center section 210 has nofuselage or mission module attached or mounted to it. Instead, allmission equipment is stowed internal to the center section 210,accessible via removable panels or hatches. In this manner, the drag ofthe central portion of the aircraft is reduced because there is nofuselage or mission module creating additional frontal area. Alternateunmanned aircraft 250 comprises a different right outboard wing portion252 and a different left outboard wing portion 254 from correspondingcomponents of aircraft 220 and 230. These wing portions 252, 254 can beseen to be substantially entirely flat, not having dihedral or curvatureout of plane. Right control surfaces 253 are mounted on the rightoutboard wing portion 252, while left control surfaces 255 are mountedon the left outboard wing portion. Additionally, a right boom 257 isalso attached at the right interface 216 with the center section. Theright boom 257 cooperates with a left boom 258 to support an optionalempennage 259 for providing pitch and directional stability and controlto the aircraft 250. The outboard wing portions 252, 254 are attached tocenter section 210 by means of folding mechanisms.

The folded alternate unmanned aircraft 260 allows for compact stowage.Here, the right wing portion 252 and left wing portion 254 are rotatedup over the center section 210 such that the wing tips approach theaircraft centerline 261.

Whether manned, unmanned, with folding wings or without folding wings,preferred aircraft have a mid-wing configuration, which is used hereinto mean that the wings are other than in a high or low position on afuselage (in our case the center section). As used herein, a low-wingconfiguration has the left and right wing sections structurally coupledat the bottom of or below the fuselage, and a high-wing configurationhas the left and right wing sections structurally coupled at the top ofor above the fuselage.

Thus, it is seen that any manner of workable variations can be achievedby substituting various elements of the modular aircraft kit 200. Outerwing portions of different spans, taper ratios, sweeps, airfoils, andplanforms can be substituted to tailor aircraft performance to intendedmissions. It is contemplated that some outer wing portions can havedifferent control surface configurations, with any suitable number ofslats, plain flaps, slotted flaps, or split flaps. Some outer wingportions could advantageously be equipped with large embedded antennasas needed for certain missions. Similarly, any number of variousfuselages or mission modules could be coupled to the center section 210.Such fuselages or mission modules could accommodate varied payloads withdifferent sizes and packing requirements, including, for example,passengers, pallets, munitions, radars, and RF jamming equipment. Inespecially preferred modular aircraft kits, the essential systems foraircraft functioning are contained in the center section 210 to allowfor rapid reconfiguration. In this manner, the flight control computer,standard communications equipment, navigation sensors, fuel tanks, fuelpumps, generators, electric power system, and engines are located withinthe center section 210. With contemplated mode of modular operation, anaircraft could begin its operational life with one set of originallydeployed outer wing members, and then exchange them for another,non-fungible set of outer wing members selected from an aircraft kit200.

One list of contemplated missions for a single aircraft withinterchangeable mission modules includes: aerial mapping, maritimepatrol, police surveillance, aerial spraying, air ambulance, airinterdiction, close air support, ground strike, light water bomber forfirefighting, refrigerated cargo, cargo accommodations with a rollerfloor and tie downs, combination cargo and passenger transport, air dropcargo, standard passenger transport, luxury passenger transport,communications relay, radio frequency signal jamming or interception,missile launch, and small vehicle launch.

FIG. 3 is a perspective exploded view illustration of an alternatepreferred aircraft center section 310 showing the supporting structureand key mechanical systems. The alternate preferred aircraft centersection 310 comprises a supporting substructure, including a forwardspar 340, an aft spar 342, a right center spar 344, a left center spar346, right and left inboard ribs 350, 351, right and left second ribs352, 353, right and left third ribs 354, 355, and right and leftoutboard ribs 356, 357. In this preferred embodiment, both the forwardspar 340 and aft spar 342 are curved and run between a left interface315 of the center section 310 and a right interface 316. These sparsserve as the primary structural members to react forces generated bylifting surfaces on the center section 310 and from outboard wingmembers (not shown).

The forward spar 340, aft spar 342, right inboard rib 350, and leftinboard rib 351 define a central cavity 380 that can accommodatepayloads or cargo, and has unobstructed access both upward and downwardin a conventional flight orientation (when no skin panels, missionmodules, or fuselage modules block this access). This upward anddownward access is useful for sensor range of sight, launchingmunitions, maintenance access, air drop of cargo, and installation offuselage modules or payloads that require a depth dimension greater thanthe maximum depth of forward and aft spars 340, 342. The central cavity380 has a centerline cavity length 398 and a maximum cavity width 396.Notably, to achieve the open central cavity 380, the right center spar344 must terminate at the right inboard rib 350 while the left centerspar 346 terminates at the left inboard rib 351. One of ordinary skillin the art would not contemplate a discontinuous center spar, becausethe highest bending moments and stresses occur near the center of a wingstructure. Normally, structural members have the greatest dimensions(height, depth, and thickness) where bending moments and stresses arehighest because this yields a more efficient and lower weight structure.Termination of major structural member (such as the left and rightcenter spars 344, 346) at the point of greatest bending moment does notfollow from best engineering practices. At its outer extent, near theright interface 316 of the center section 310, the right center spar 344splits into a y-shape to better support a right outer wing portion.

Overall, the center section has a center span 392 between the leftinterface 315 and right interface 316. Depending on the nature of theouter wing portions (not shown) selected for attachment to the centersection 310, the assembled aircraft can have a total span that issubstantially greater than the center span 392 of the center section310, including, in preferred embodiments, an overall span that is 2×,2.5×, 3×, 3.5×, or even 4× the span 392 of the center section 310. Thesubstructure of the center section 310 also has a substructure length394 between the aftmost portion of the aft spar 342 and the foremostportion of the forward spar 340. In preferred embodiments, thesubstructure length 394 is greater than the cavity length 398 andbetween 1.25×, 1.5×, 1.75×, 2×, 2.5×, and 3× the cavity width 396. Inthis instance, and where other upper limits are not expressly stated,the reader should infer a reasonable upper limit. In this instance, forexample, a commercially reasonable upper limit is about 5× the cavitywidth.

The substructure of the center section 310 advantageously supportsaerodynamic fairing elements including a right leading edge portion 311,a right trailing edge portion 313, and upper surface skin panels 308,309. These fairing elements cooperate to serve as a portion of thecenter section 310 for generating lift, having a total area (left andright sides) at least equal to the product of the cavity length 398 andcavity width 396.

The center section 310 and its substructure also carry a variety ofsystems essential to the functioning of an aircraft. In preferredembodiments, the center section 310 supports at least one engine inlet322, a left side engine 324, a generator 328, and an exhaust duct 326.For clarity, in FIG. 3, only the left side engine 324 is shown.Cooperatively, the left side engine 324 and right side engine (notshown) provide adequate thrust to sustain level flight of an assembledaircraft. In some preferred embodiments, the left and right enginescooperate to provide a maximum thrust that is not greater than 20%, 30%,40% or 50% of the maximum takeoff weight of the aircraft. In somepreferred embodiments, the engine 324 is installed in such a manner thatit does not extend above or below the center section 310, even ifportions of an inlet or exhaust might extend above the center section.Additionally, a set of left fuel tanks 360 and right fuel tanks (notshown) provide fuel supply to the aircraft engines. An exemplary fueltank 362 is supported by a combination of spars, ribs, and skin panelswhen installed in the center section 310. In some preferred embodiments,the total fuel capacity of the aircraft in pounds is greater than themaximum takeoff weight of the aircraft in pounds. Preferred aircraft arealso equipped with a four leg landing gear system entirely housed in thecenter section 310 when retracted, and comprising a right main leg 370,a left main leg 371, a right nose leg 372, and a left nose leg 373. Theleft and right nose legs 372, 373 provide a steering capability.

For modularity, the center section 310 is advantageously constructed tosupport interchangeable mission modules, fuselages, and outer wingportions. In preferred embodiments, a left outer wing portion (notshown) is supported by a folding system including a set of right forwardfolding attachments 336 and right aft folding attachments 338 thatrotatably support an outer wing portion, and react the considerableflight bending moments generated by an outer wing portion into theforward spar 340, aft spar 342, and left center spar 346. The centersection 310 also supports a variety of mission modules or fuselages bymeans of hardpoints 332, 334 that allow mission modules to bemechanically fastened in a manner that facilitates quick disconnectionand reconnection while still reacting loads.

In especially preferred embodiments, the aft spar 342, forward spar 340,and center spars 344, 346 are of carbon-epoxy composite construction.The caps of the forward spar 340 and aft spar may comprise high moduluscarbon fibers in pultruded form. Hardpoints 332, 334 and foldingattachments 336, 338 are preferably constructed of high strength metalincluding for example titanium or steel.

FIG. 4 is a schematic top-view illustration of a flight-operable,modular aircraft 400 having an operational life. Some contemplatedoperational lives include 2000 hours 3000 hours, 5000 hours, 10000 hours20000 hours, 30000 hours, 50000 hours, of flight time. An aircraftcenter section 410 couples to a right outer wing member 402 and a leftouter wing member 404. The outer wing members installed at the start ofthe aircraft's operational life are said to be originally deployed. Theleft and right outer wing members are advantageously each sized andconfigured to provide at least 12, 15, 20, 25, 30, or 35% of the totallift of the aircraft during at least some portion of substantiallystraight and level cruise flight. In preferred embodiments, the centersection 410 is shaped and configured to produce at least 20, 25, 30, 35,40, and 50% of the total lift of the aircraft during the same portion ofthe cruise flight. An aircraft flight will typically comprise takeoff,climb, cruise, an optional loiter, cruise, descent, and landing insequence. A cruise flight condition means sustained self-powered flightat a given cruise altitude and cruise speed. Contemplated cruisealtitudes include 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, and 65thousand feet above sea level. Contemplated cruise speeds correspond toMach numbers of 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75,0.8, 0.85, and 0.9.

The right outer wing member 402 comprises a spar 426 for structuralsupport, a control surface 403 to assist in trim and control of themodular aircraft 400, an actuator 470 to drive the control surface 403,and wiring 472 to carry power and command signals from a flight controlcomputer 462 located in the aircraft center section 410. In somepreferred embodiments, the originally deployed left outer wing member404 is substantially a mirror image of the originally deployed rightouter wing member 402, and also comprises a left control surface 405 andleft spar 427. It is contemplated that preferred modular aircraft 400could exchange an originally deployed right outer wing member 402 areplacement right outer wing member 406 that is not fungible with theoriginally deployed right outer wing member 402. At the same time,flight control laws, as codified and executed in the flight controlcomputer 462, would adapt to this change of wing members as necessary.

The center section 410 is built around an aircraft core 490, an elementadvantageously configured to enable aircraft system modularity. Theaircraft core 490 comprises a forward curved spar member 422, an aftcurved spar member 424, and left and right hardpoints 432, 430 thataccommodate attachment of outer wing members, folding of outer wingmembers, and are located in the immediate vicinity of connections forelectrical power or signals for powering the outer wing members. Thehardpoints 430, 432 serve as wing couplings adapted to couple ordecouple outer wing members 402, 404 during the operational life of theaircraft. The right wing hardpoint 430 can be viewed as a coupling thatcarries load between a composite spar 426 of the detachable right outerwing member 402, and the fore and aft curved spars 422, 424,respectively. The hardpoints 430, 432 can also be advantageouslyconfigured as hinges to allow folding of the outer wing members 402, 404for compact stowage. The aircraft core 490 is also advantageouslyequipped with forward hardpoints 491 that serve a forward couplingadapted to couple or decouple a fuselage or mission module to the centersection 410 during the operational life. In preferred embodiments, theforward hardpoints 491 are attached to the curved forward spar 422. Afthardpoints 492 may cooperate with forward hardpoints 491 in supportingor coupling a fuselage 480, mission module, or payload to the aircraftcore 490 and center section 410.

The preferred modular aircraft 400 is optionally equipped with afuselage 480. Preferred fuselages 480 are optional and can be coupled ordecoupled from the aircraft during the operational life. Fuselage 480 isequipped with a cockpit 482 comprising an on-board pilot interface andmeans for on-board pilot control, including instrumentation and displayscreens 482, inceptors 486, and an ejection seat 487. Fuselage 480 isequipped with forward mounts 488 and aft mounts 489 which couple toaircraft forward hardpoints 491 and aft hardpoints 492 to support theoptional/removable fuselage 480, and allow the installation or removalof the fuselage in less than two hours. Other fuselages or missionmodules are contemplated, including those without cockpits or means foron-board pilot control, which can couple to the aircraft 400 using thesame forward and aft hardpoints 491, 492 such that fuselages can bechanged out during the operational life of the aircraft 400. Inpreferred embodiments, the fuselage coupling or the wing coupling thatattaches the right outer wing member 402 to the center section 410 alsocarries electrical connections. In especially preferred embodiments, aquick disconnect connector is located within two feet of a structuralhardpoint. Some preferred fuselages 480 or mission modules are equippedwith a targeting system 441 such as a radar that is operable by each ofa pilot in the cockpit and also by a ground controller.

It is further contemplated that in some especially preferredembodiments, mission modules need not be a single-piece fuselage. Themodular nature of the aircraft core 490 having a series of couplings andhardpoints allows it to be viewed as a multi-way receptacle foraccessories, including a nose portion of a mission module that couldattach to forward hardpoints 491 or other couplings, a tail portion of amission module that could attach to aft hardpoints 492 or othercouplings, optionally a central portion of a mission module, skinpanels, a first outer wing portion, a second outer wing portion, andvarious leading edge and trailing edge pieces. In this manner, missionequipment and mission modules can be rapidly tailored to meet emergingneeds, without the requirement of having to change an entire fuselage.In some instances, only the nose portion of a fuselage or mission modulemight be interchanged, for example to accommodate an alternate targetingsystem 441.

The aircraft core 490 also has a leading edge coupling 496 to supportattachment of a removable leading edge 522, and a trailing edge coupling497 to support attachment of a removable trailing edge 524. This enablescoupling or decoupling right and left leading edge portions during theoperational life of the aircraft, where the leading edge portions areconfigured to assist in providing lift to the aircraft during the atleast some portion of cruise flight. The center section 410 of theaircraft 400 comprises an aircraft core 490 as well as a leading edgefairing 522 and trailing edge fairing 524. The aircraft core 490comprises a right engine 436 and a left engine 438 which cooperate toprovide a propulsive force for the aircraft. In preferred embodiments,the engines 436, 438 are installed such that they do not extend above orbelow the center section 410 skin surfaces. A preferred installation ofthe right engine 436 involves support from a right inboard rib 494 orfrom an upper surface extension of a right center spar that does notextend across the central cavity 499 such that the engine that is notstructurally supported from directly below the engine.

It is thus seen that, in some preferred embodiments, the central cavity499 of the aircraft core 490 can be viewed as an open bay entirelyinside the aircraft, and supported on only four sides by a fore and aftspar and left and right inboard ribs. In such instances, the centralcavity 499 is free from supporting structural members such as sparsrunning laterally across, through, above, or below the central cavity499. While many such aircraft could benefit from such structuralsupporting members to provide strength and stiffness near the centerlineof the aircraft where bending moments are high, the present inventivesubject matter contemplates eliminating all such supporting members inorder to create a flexible and modular central cavity 499 which canaccommodate any manner of payloads. In preferred embodiments, even skinor door surfaces which may be installed above or below the centralcavity 499 to provide an aerodynamic fairing for reduced drag, arenon-structural, and carry no more than 2% or 5% of the total bendingmoment across the centerline of the aircraft.

The aircraft core 490 also contains one or more flight control computers462, and one or more sensors 466, and communications that cooperate toserve as avionics sufficient to operate the aircraft without receivingcontrols from outside the center section 410. Preferred aircraft 400have center sections 410 that contain substantially all of the avionicsfunctionality and are advantageously equipped with fault-tolerant flightcontrol computers and redundant sensors that communicate via an aircraftnetwork bus. Preferred aircraft are also advantageously equipped withone or more communications devices 464, including for example,line-of-sight datalinks, voice radios, beyond-line-of-sight datalanks,transponders, satellite communications radios, and other data radios. Inpreferred embodiments, the communications devices 464 allows forreceiving communications and commands from off-board persons or devicesas well as the transmission of flight data and sensor data to off-boardpersons or devices. In some contemplated aircraft, the flight controlcomputers 462 are capable of receiving inputs or commands from either orboth on-board pilot control and ground control such as a ground station.In instances where the flight control computers 462 receive input fromboth off-board and on-board pilots, the flight control computers 462advantageously act as an arbiter to determine which set of inputs drivethe vehicle core flight control. In especially preferred embodiments,the aircraft core 490 is equipped with substantially all of the systemscontent required to fly the aircraft 400 except for flight controlsurfaces and their actuation. This segregation of systems content helpsenable overall aircraft modularity.

The aircraft core 490 is further advantageously equipped with left andright forward landing gear 451, 450 and left and right aft landing gear453, 452 that attach to ribs or spars 422, 424 via hardpoints. Thesefour landing gear members are preferably retractable and areadvantageously configured to retract into the center section 410 suchthat they do not extend further forward of the forward curved spar 422or further aft of the aft spar 424, and are entirely bounded by thestructural elements and skins of the center section 410 when in thefully retracted position. Some preferred aircraft cores 490 resemble atrapezoid, resulting from the cooperation of the forward curved spar422, aft curved spar 424, right hardpoint 430, left hardpoint 432, andleft and right inboard ribs 493, 494 in providing structural support forthe aircraft's operations.

The aircraft core 490 is advantageously equipped with a fuel supply 437such as one or more fuel tanks operationally coupled to the propulsiveengines 436, 438. The total fuel supply is preferably distributed bothto the right and the left of the central cavity 499, and the engines436, 438 are preferably disposed on either side of the central cavity499. It is contemplated that the fuel supply 437 can be sized andconfigured to house at least 80% or at least 90% of the aircraft totalfuel and be housed entirely within the bounds of the aircraft centersection.

In preferred embodiments, the horizontally curved forward spar 422 andhorizontally curved aft spar 424 are major structural elements bridgingthe loads generated by left and right outboard wing members 404, 402.Each of the two carries at least 30% and at most 70% of the bending loadduring at least some portion of substantially straight and level cruiseflight. In especially preferred embodiments, the spars 422, 424 are madeof carbon-epoxy composite and are constructed in pre-curved molds andrun continuously and laterally between a right wing coupling 430 and aleft wing coupling 432. A right inboard rib 494 and left inboard rib 493run longitudinally between the forward spar 422 and the aft spar 424.The aircraft core 490 thus comprises forward and aft curved compositespars 422, 424, and right and left inboard ribs 493, 494, the spars andribs operatively coupled to provide the centerline central cavity 499.

With reference to both FIG. 4 and FIG. 5, which depict differentconfigurations of the same flight-operable modular aircraft 400, thecentral cavity 499 has a width dimension 514 and a length dimension 512as well as a depth and an internal volume. In preferred embodiments, thewidth dimension 514 is at least 3%, 4%, 5%, 7%, or 9% of the total span502 of the flight-operable modular aircraft 400, and at most 10%, 15%,or 20% of the span 502. The length dimension 512 is at least 15%, 20%,25%, 30%, 40%, 50% or 60% of the total length 510 of the aircraft 400and at least 70% of the length of the aircraft core 490. In preferredembodiments, the central cavity has a cargo coupling 495 that isconfigured and dimensioned to carry an interchangeable payload 440.Contemplated interchangeable payloads include an ordnance launcher, asurveillance payload, electronic countermeasures, and other sensors, RFequipment, and munitions.

FIG. 5 is a schematic top-view illustration of an alternateconfiguration of the preferred modular aircraft of FIG. 4, without theoptional fuselage 480 installed and without showing many of the internalsystems contained in the aircraft core 490. In this view, the aircraft400 is equipped with no fuselage, a right outer wing member 402, a leftouter wing member 404 removable leading edges 522, 523 and removabletrailing edges 524, 525. A payload is carried in the internal centralcavity 499. The internal central cavity 499 is preferably covered by oneor more non-structural skin panels 580 such that the central cavity 499has no overhead structural support. In preferred embodiments, there isno structural support above or below the central cavity 499. In someembodiments, the bottom of the internal cavity may be covered by movingpayload doors. Preferred central cavities 499 extend vertically to anupper skin and a lower skin or non-structural payload doors. Otherportions of the aircraft core 490 may be covered by one or more skinpanels 581. The skin panels 581 may have provisions for engine inlets571, 572 and engine exhausts 573, 574 that cooperate to allow air toflow through engines 436, 438 even if the engines 436, 438 have a buriedinstallation and are housed between the upper and lower skins of thecenter section 410.

The aircraft 400 has a total span 502 that is the sum of a center span506 associated with the center section 410, a right span 504 associatedwith the right outer wing member 402 and a left span 508 associated withthe left outer wing member 404. The center section extends laterallybetween the left and right attachments for the outer wing members 402,404. Left and right are defined relative to a centerline 590 of theaircraft 400. Preferred total spans of the aircraft are between 30 and180 feet, between 50 and 160 feet, between 70 and 140 feet, and between90 and 130 feet, or least 80 feet, or at least 100 feet. Due to themodular nature of the aircraft 400, the total span 502 of the aircraft400 can change during its operational life.

It is contemplated that, despite the considerable total span asdescribed above, some preferred aircraft 400 can be constructed in sucha way that the overall vehicle, comprising forward and aft curvedcomposite spars 422, 424 and right and left outboard wing members 402,404 has sufficient stiffness to produce a natural frequency of no lessthan 5 Hz or no less than 6 Hz when airborne. This high structuralstiffness can advantageously delay or prevent aeroelastic flutter fromoccurring.

As shown, the aircraft 400 of FIG. 5 is shaped as a flying wing, havingsubstantially no empennage, no horizontal tail, and no vertical tail.Some preferred aircraft are substantially flat, having a dihedral oranhedral of no more than ten degrees, and a maximum thickness-to-chordratio of no more than thirty percent. Elements of FIG. 4 and FIG. 5could be combined to form a kit. One exemplary kit could comprise aflight-operable modular aircraft 400 without an originally deployedfuselage, as well as an optional/removable fuselage 480, a right outerwing member 406 that is non-fungible with an originally deployed rightouter wing member 404, and a leading edge portion 522.

In preferred embodiments, the wing coupling that attaches the rightouter wing member 402 to the center section 410 also carries electricalconnections. In especially preferred embodiments, a quick disconnectconnector is located within two feet of a structural hardpoint.

FIG. 6 is plot of the lift distribution of the preferred modularaircraft of FIG. 5 at a cruise flight condition. The horizontal axis 602extends from the left semi-span of the aircraft 400 to the rightsemi-span of the aircraft 400. The vertical axis 604 is non-dimensionaland represents the local lift coefficient for curve 610 and the productof local chord and local lift coefficient divided by the chord at theright extent of the center section (c×c₁/c_(ref)) for curve 620. Curve620 is proportional to dimensional local lift at a wing section. Thus,shaded area 622 represents the total lift generated by the left outerwing member 404, shaded area 626 represents the total lift generated bythe right outer wing member 402, and shaded area 624 represents thetotal lift generated by the center section 410. In preferred embodimentswhere the aircraft 400 is a flying wing, substantially all of the liftis generated by these three sections together. In especially preferredembodiments, the center section generates between 30% and 70% or between40% and 60% of the total lift of the aircraft during sustained flight ata substantially straight and level cruise condition.

FIG. 7 is a perspective view illustration of an exceptionally preferredaircraft left interface assembly 700, 215 or 315 of center section 210,310 or 410 and a modular outer wing section 224, 254 or 404. Themulti-shear, steel or titanium fittings 751, 752, shown as hardpointsand folding attachments 336, 338 or 432 carry loads from the outboardmodular outer left wing to the center section. The inboard fittings 751are permanently fastened to the inboard spars 740 and the outboardfittings 752 are permanently fastened to the outboard spars. The inboardfittings 751 and outboard fittings 752 are mechanically fastened viareusable attachment hardware. Each inboard and outboard fitting pair isjoined via a pin which is rapidly inserted to or extracted from thefittings 751, 752 via a hydraulic actuator 720. Extraction of thehydraulic pins 720 from the fittings 751, 752 allows the especiallypreferred outer left wing module 224, 254 or 404 to fold. Removal of twoadditional pins 731 allows complete removal or replacement of the outerleft wing module. All hardware used to fold, remove and assemble theouter left wing is reused for the continued operation of the aircraft;no hardware is modified, repaired or discarded as part of the folding,removal of replacement.

FIG. 8 is a perspective view illustration of an exceptionally preferredembodiment of forward and aft hardpoints 810, 332, 334, 491 or 492 ofcenter section 210, 310 or 410. Four of the aluminum or titaniumhardpoints 810 are located on the forward curved spar 830, 340 or 422and four (preferably identical hardware) are located on the aft curvedspar 840, 342 or 424. Each attachment is permanently fastened to theprimary structure via the forward 830 or aft 840 spar and the leftinboard rib 820, 351 or 493 or the right inboard rib 821, 350 or 494.The front and aft hardpoints provide for attachment and removable offuselage 480 and provide for attachment and removable of aninterchangeable payload 440 in the aircraft open central cavity 380 or499 via reusable attachment hardware. All hardware used to remove andassemble the fuselage is reused for the continued operation of theaircraft; no hardware is modified, repaired or discarded as part of theremoval of replacement.

At a nominal, non-accelerating cruise flight condition, the aircraftlift is approximately equal to its weight. If the aircraft is notrefueled or resupplied in flight, the weight in cruise is less than theweight at takeoff. Aircraft conventionally have a maximum takeoffweight, which is the greatest weight at which the aircraft can safelytakeoff. Under normal operation, without refueling or resupply, theaircraft weight will continuously decrease until landing as fuel isburned. Powered aircraft are conventionally equipped with a fuel supplycapable of holding a maximum quantity of fuel. It is contemplated thatsome preferred aircraft 400 without provisions for aerial refuelingcould be equipped with a fuel supply 437 sized and dimensioned with fuelcapacity greater than maximum takeoff weight. In this manner, theaircraft would be not be able to takeoff with its fuel supply 437 filledto capacity. One of ordinary skill in the art simply would not think ofover-sizing the fuel supply to such a degree, because there is noperceptible benefit. The present inventive subject matter, however,contemplates that an aircraft core 490 could accommodate future growthof an aircraft 400 in this manner.

It should be apparent to those skilled in the art that many moremodifications besides those already described are possible withoutdeparting from the inventive concepts herein. The inventive subjectmatter, therefore, is not to be restricted except in the spirit of theappended claims. Moreover, in interpreting both the specification andthe claims, all terms should be interpreted in the broadest possiblemanner consistent with the context. In particular, the terms “comprises”and “comprising” should be interpreted as referring to elements,components, or steps in a non-exclusive manner, indicating that thereferenced elements, components, or steps may be present, or utilized,or combined with other elements, components, or steps that are notexpressly referenced. Where the specification claims refers to at leastone of something selected from the group consisting of A, B, C . . . andN, the text should be interpreted as requiring only one element from thegroup, not A plus N, or B plus N, etc.

What is claimed is:
 1. A flight-operable, modular aircraft comprising: acenter section having a cargo bay, and fore and aft spars positionedfore and aft of the cargo bay, respectively; and left and right wingsthat are structurally coupled together at least predominantly throughthe fore and aft spars; wherein the center section provides a least 25%of the lift of the aircraft during at least some portion of cruiseflight the aircraft has a wing span of at least 80 ft, and has left andright wings having sufficient stiffness to produce a natural frequencyof no less than 6 Hz.
 2. The aircraft of claim 1, wherein the wings arecoupled to the center section in a mid-wing configuration.
 3. Theaircraft of claim 1, wherein the wings are coupled to the fore and aftspars using reusable attachment hardware comprising at least one of pinsand bolts.
 4. The aircraft of claim 3, wherein the wings are foldingwings.
 5. The aircraft of claim 1, wherein the center section having acargo bay that is structurally open to top and bottom, and is boundedforward and aftward by the fore and aft spars, respectively.
 6. Theaircraft of claim 1, further comprising left and right ribs structurallycoupled to the fore and aft spars, and wherein the cargo bay is boundedby the fore and aft spars, and the left and right ribs.
 7. The aircraftof claim 1, wherein the fore spar has hard points for connecting a nosesection, and the aft spar has hard points for connecting a tail section,and each of the hard points uses at least one of pins and bolts.
 8. Theaircraft of claim 7, wherein bending loads resulting from the nose andtail section are structurally carried by left and right ribs.
 9. Theaircraft of claim 1, wherein the fore spar extends across an entirefirst width of the center section.
 10. The aircraft of claim 9, whereinthe fore spar is curved across the entire first width, and comprises acomposite material.
 11. The aircraft of claim 9, further comprising anaft support that includes comprises a second curved spar that extendsacross an entire second width of the center section.
 12. The aircraft ofclaim 1, further comprising right and left inboard ribs, and wherein thecenter section has a trapezoidal shape defined by the right and leftinboard ribs and the fore and aft spars.
 13. The aircraft of claim 1,wherein the fore spar is curved across an entire first width of thecenter section, the aft spar is are curved across an entire secondsection.
 14. The aircraft of claim 1, wherein the aircraft is shaped asa flying wing, having substantially no empennage, no horizontal tail,and no vertical tail.
 15. The aircraft of claim 1, wherein the centersection includes an engine that provides a propulsive force for theaircraft, and wherein the engine does not extend above or below thecenter section.
 16. The aircraft of claim 1, wherein center sectionincludes avionics capable of operating the aircraft through both groundcontrol and on-board pilot control, and fault-tolerant flight controlcomputers and redundant sensors that communicate via an aircraft networkbus.
 17. The aircraft of claim 1, further comprising first, second, andthird landing gear that retract into the center section.
 18. Theaircraft of claim 1, further comprising a cockpit, and a targetingsystem operable by each of a pilot in the cockpit and a groundcontroller.
 19. The aircraft of claim 1, further comprising a supply offuel, wherein the center section is an interchangeable mission modulethat houses at least 80% of onboard fuel.